The present invention relates to a single crystal material supplying, apparatus and a single crystal material supplying method for heating and melting a single crystal material in an auxiliary crucible and for supplying the melt to a main crucible in a single crystal pulling apparatus for manufacturing dislocation-free single crystal of silicon (Si) by Czochralski pulling method.
In general, in a single crystal manufacturing apparatus based on Czochralski pulling method, the pressure in a highly pressure-resistant airtight chamber is reduced to about 10 torr and fresh argon (Ar) gas is supplied into it, and polycrystal in a quartz crucible installed in the lower portion of the chamber is heated and melted. A seed crystal is immersed from above into the surface of the melt. Then, the seed crystal and quartz crucible are rotated and moved up and down, and the seed crystal is pulled so that a single crystal (the so-called ingot) is grown, which comprises an upper cone portion in conical shape with its upper end protruding under the seed crystal, a body portion in cylindrical shape, and a lower cone portion in conical shape with its lower end protruding.
As a conventional method to melt the raw material in an apparatus as described above, a method for supplying raw material to supplement the decrease of the melt in a crucible (hereinafter referred as xe2x80x9cmain cruciblexe2x80x9d) for pulling up single crystal has been proposed. For example, JP-A-55-130894 discloses a method for melting raw material in an auxiliary crucible communicated with a main crucible and for additionally supplying the melt from the auxiliary crucible to the main crucible via a communicating pipe. Also, JP-A-56-164097 describes a method for supplying and melting solid raw material in an auxiliary crucible in a pulling apparatus from outside the pulling apparatus and for additionally supplying the melt from the auxiliary crucible to the main crucible.
However, in the method to continuously supply the melt from the auxiliary crucible to the main crucible via the feeding pipe in small quantity by overflow, there must be provided heating means such as heater or heat keeping means such as heat insulating material on outer periphery of the feeding pipe to prevent solidification of the melt in the feeding pipe. There is another method to melt a bar-like raw material by suspending it and to feed the melt by dropping without using the feeding pipe, but the raw material must be formed in bar-like shape in advance and it is also disadvantageous in that the feeding speed is low.
To solve the above problems, it is an object of the present invention to provide an apparatus and a method by designing in such manner that the melt in the auxiliary crucible overflows intermittently into an opening on the upper end of the feeding pipe and additional raw material is supplied intermittently in the auxiliary crucible so that overflow quantity is increased or that additional raw material is continuously supplied into the auxiliary crucible but surface tension of the melt in the auxiliary crucible itself is increased and the melt rises up above the opening of the pipe so that a predetermined quantity of the melt overflows at one time, or the above two procedures may be combined.
Specifically, the present invention provides a single crystal material supplying apparatus for heating and melting a single crystal raw material in an auxiliary crucible and for supplying the melt into a main crucible via a feeding pipe, characterized in that:
the apparatus comprises raw material supply means for supplying additional raw material intermittently into the auxiliary crucible in such quantity that the melt overflows intermittently into an opening at the upper end of the feeding pipe after the raw material in the auxiliary crucible has been melted.
Also, the present invention provides a single crystal material supplying apparatus for heating and melting a single crystal raw material in an auxiliary crucible and for supplying the melt into a main crucible via a feeding pipe, characterized in that:
edge of an opening on the upper end of the feeding pipe is deformed in such manner that the melt in the auxiliary crucible rises up to a given height above the opening at the upper end of the feeding pipe due to surface tension.
Further, the present invention provides a single crystal material supplying apparatus for heating and melting a single crystal raw material in an auxiliary crucible and for supplying the melt into a main crucible via a feeding pipe, characterized in that:
a high frequency coil for heating the raw material in the auxiliary crucible is arranged around the auxiliary crucible so that the melt in the auxiliary crucible rises up to a given height above the opening on the upper end of the feeding pipe due to convection.
Also, the present invention provides a single crystal material supplying apparatus for heating and melting a single crystal raw material in an auxiliary crucible and for supplying the melt into a main crucible via a feeding pipe, characterized in that:
the apparatus comprises raw material supply means for supplying additional raw material intermittently into the auxiliary crucible in such quantity that the melt overflows intermittently into the opening on the upper end of the feeding pipe after the raw material in the auxiliary crucible has been melted; and
edge of the opening on the upper end of the feeding pipe is deformed in such manner that the melt in the auxiliary crucible rises up to a given height above the opening on the upper end of the feeding pipe due to surface tension.
Further, present invention provides a single crystal material supplying apparatus for heating and melting a single crystal raw material in an auxiliary crucible and for supplying the melt into a main crucible via a feeding pipe, characterized in that:
the apparatus comprises raw material supplying means for supplying additional raw material intermittently into the auxiliary crucible in such quantity that the melt overflows intermittently into the opening on the upper end of the feeding pipe after the raw material in the auxiliary crucible has been melted; and
a high frequency coil for heating the raw material in the auxiliary crucible is arranged around the auxiliary crucible so that the melt in the auxiliary crucible rises up to a given height above the opening on the upper end of the feeding pipe due to convection.
Also, the present invention provides a single crystal material supplying apparatus for heating and melting a single crystal raw material in an auxiliary crucible and for supplying the melt into a main crucible via a feeding pipe, characterized in that:
a high frequency coil is arranged around the auxiliary crucible so that the melt in the auxiliary crucible rises up to a given height above the opening on the upper end of the feeding pipe due to convection; and
edge of the opening on the upper end of the feeding pipe is deformed in such manner that the melt in the auxiliary crucible rises up to a given height above the opening on the upper end of the feeding pipe due to surface tension.
Also, the present invention provides a single crystal material supplying method for heating and melting a single crystal raw material in an auxiliary crucible and for feeding the melt into a main crucible via a feeding pipe, characterized in that the method comprises the step of:
feeding additional raw material intermittently into the auxiliary crucible in such quantity that the melt overflows intermittently into the opening on the upper end of the feeding pipe after the raw material in the auxiliary crucible has been melted.
Further, the present invention provides a single crystal material: supplying method for heating and melting a single crystal raw material in an auxiliary crucible and for feeding the melt into a main crucible via a feeding pipe, characterized in that the method comprises the step of:
increasing surface tension of the melt after the raw material in the auxiliary crucible has been melted.
Also, the present invention provides a single crystal material supplying method for heating and melting a single crystal raw material in an auxiliary crucible and for feeding the melt into a main crucible via a feeding pipe, characterized in that the method comprises the steps of:
feeding additional raw material intermittently into the auxiliary crucible in such quantity that the melt overflows intermittently into the opening on the upper end of the feeding pipe after the raw material in the auxiliary crucible has been melted; and
increasing surface tension of the melt after the raw material in the auxiliary crucible has been melted.